1. Field of the Invention
The present invention relates to a developing method, a developing apparatus and a storage medium, for use in developing a substrate having a surface that has been coated with a resist and exposed to light.
2. Background Art
In a photo-resist step that is one of steps for producing semiconductors, a resist pattern is formed by coating the resist on the surface of each semiconductor wafer (hereinafter, referred to as a “wafer”), exposing the coated resist to light via a predetermined pattern, and finally developing the resist. Such a process is generally carried out by using a system, in which an exposure apparatus is connected with a coating and developing apparatus adapted for coating and developing the resist.
In a typical example of conventional developing processes, the wafer is held, horizontally, on a substrate holding part, and a developing solution nozzle having fine discharging holes formed therein is then located in a position slightly separated or floated away over the wafer surface. Thereafter, the wafer is rotated about a vertical axis, while the developing solution nozzle is moved in a radial direction relative to the rotation of the wafer, with the developing solution being discharged from the developing solution nozzle. Thus, the developing solution can be supplied onto the wafer surface in a spiral state. After being supplied with the developing solution in such a manner, the wafer is held at rest until a predetermined developing time passes by. Then, a rinsing liquid is supplied onto the wafer in order to wash away the developing solution. Such a developing process is commonly referred to as a paddling-type developing method.
However, such a paddling-type developing method requires a greater amount of the developing solution. To address this problem, another method, as described in Patent Document 1, for performing the developing process, by discharging the developing solution onto the substrate while rotating the substrate, has been studied. Now, this developing method will be described in brief with reference to FIGS. 14(a), 14(b). First, the wafer W is rotated about the vertical axis via a spin chuck 22 that is the substrate holding part, while the developing solution nozzle 13 is moved from a peripheral portion toward a central portion of the wafer W, wherein the developing solution nozzle 13 includes a slit-like discharging hole 12 extending in a direction from the peripheral portion toward the central portion of the wafer W, as is shown by an arrow in the drawing. During this operation, the developing solution 14 is discharged, in a ribbon-like state, from the discharging hole 12, as such the developing solution 14 can be supplied onto the surface of the wafer W, in a spiral state. In this way, the whole surface of the wafer W can be covered with a liquid film or layer 15 of the developing solution 14. Even after the developing solution nozzle 13 has reached a position above the central portion of the wafer W and the whole surface of the wafer W has been covered with the developing solution 14, the developing solution nozzle 13 should continue to supply the developing solution 14 onto the central portion of the wafer W in order to prevent the liquid film 15 from being dried up. After a while, once the resist pattern is formed in the resist on the wafer surface by the developing process, the rinsing liquid is discharged onto the resist by a rinsing nozzle (not shown) so as to wash away the developing solution 14. In this way, the developing process is completed.
In the case of forming the liquid film 15 of the developing solution 14 on the wafer W, by employing the developing process, as described above, for discharging the developing solution onto the substrate from the nozzle while rotating the substrate, reduction of the time required for the developing process has been aimed at, by setting a transfer speed of the developing solution nozzle 13 at a greater value, as compared with the aforementioned paddling-type developing method for supplying the developing solution 14 onto the wafer surface. In addition, saving of the developing solution 14 has been attempted, by reducing the film thickness of the developing solution 14 on the wafer surface, as compared with the paddling-type developing method. However, when attempting to suppress occurrence of a developing defect or defect in a developed state and ensure uniformity of a preferred CD (i.e., a width of lines in the resist pattern), some resist materials may substantially restrict a process margin. Thus, in some cases, such a developing process, as described above, that aims at significant reduction of the developing time and/or developing solution cannot be applied adequately. Accordingly, substantial reduction or saving of the developing time and developing solution is still a challenge to be studied in performing the developing process.
In order to stabilize a shape of the resist pattern formed after the developing process in the developing method described above, a time in a range of from 10 to 20 seconds is required for removing the liquid film 15, by using the rinsing liquid, after the whole surface of the wafer W has been covered with the liquid film 15. During this period of time, the supply of the developing liquid should be continued, only in a smaller amount, for preventing the drying up of the liquid film 15 already formed. Nevertheless, if the supply of the developing solution 14 is continued, in the same amount that is used for forming the liquid film 15, the attempt of reducing the amount of the developing solution 14 used would not be achieved enough.
Accordingly, it might be envisioned to provide the developing method or apparatus that can optionally change the supply amount of the developing solution from a developing solution supply pipe 16 to the developing solution nozzle 13, in order to substantially reduce the amount of the developing solution discharged from the discharging hole 12 after the formation of the liquid film 15 on the whole surface of the wafer. However, the developing solution nozzle 13 is designed, in itself, such that the flowing speed and supplying pressure of the developing solution can be kept constant at any point in a longitudinal direction of the discharging hole 12, with the developing solution supplied in a predetermined amount. Namely, with such a design, the developing solution can be supplied, stably, in a ribbon-like state, onto the wafer W. Therefore, if the developing solution is supplied to the developing solution nozzle 13, in a smaller amount than the predetermined amount, the discharge of the developing solution 14 from the discharging hole 12 should be unstable, thus making it difficult to perform a normal and adequate developing process, leading to occurrence of the developing defect and/or significant dispersion in the resist pattern.
Accordingly, while the Patent Document 1 describes one aspect of the method for supplying the developing solution several times onto the substrate, it does not teach any measure for addressing the above problem.
Patent Document 1: TOKUKAI No. 2005-210059 (Paragraph [0044], FIG. 5, etc.)